Silicosis shows progressive massive fibrosis (PMF) with 'eggshell' calcification of hilar lymph nodes on CXR. The key pathological mechanism by which silica particles cause fibrosis involves:
- A Direct toxic injury to type II pneumocytes causing surfactant deficiency
- B Th2-mediated eosinophilic inflammation with IL-5 and IL-13 release
- C Anti-silica IgE antibody formation causing mast cell degranulation
- D Macrophage NLRP3 inflammasome activation by silica crystals releasing IL-1β, inducing fibrogenesis ✓
Explanation
Crystalline silica (especially quartz) is phagocytosed by alveolar macrophages but is cytotoxic — it disrupts phagolysosomal membranes, releasing cathepsins and activating the NLRP3 inflammasome. The inflammasome processes and releases IL-1β and IL-18, which drive macrophage activation, TGF-β secretion, and progressive fibrosis. This creates the pathological cycle: silica kills macrophages → released silica is re-phagocytosed by new macrophages → perpetual fibrogenic stimulation. Silicotic nodules (concentric whorled collagen with necrotic center) are pathognomonic. Coal workers' pneumoconiosis (CWP) has similar but less severe mechanisms.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.